1. Field of the Invention
The present invention relates to a spectroscope and spectroscopic method used to measure the spectral characteristics of a sample.
2. Description of the Related Art
Many conventional spectroscopes use a diffraction grating, and construction as illustrated in FIG. 7 is mainly adopted.
Light from a light source 101 is limited by an entrance slit 102, and is incident into a diffraction grating 103 which is rotatable. The light incident into the diffraction grating 103 is diffracted to different angles for different wavelengths. Only the light on a specific wavelength passes an outgoing slit 104. Then, the light is condensed by a condenser lens 105 and is incident into a detector 106. In a spectroscope with such construction, since a wavelength of passing the outgoing slit 104 changes by rotating the diffraction grating 103, spectrometry can be performed.
In addition, spectrometry can be performed without rotating a diffraction grating 203 by adopting construction illustrated in FIG. 8. Since a diode array is used for a detector 204 in the construction of FIG. 8, spectrometry can be performed by acquiring measurement data corresponding to each wavelength by each diode.
When rotating a diffraction grating with such construction as illustrated in FIG. 7, accuracy of angle control of a rotation angle affects accuracy of spectrometry greatly. Then, in order to raise measurement wavelength accuracy, Japanese Patent Application Laid-Open No. H07-198487 proposes a spectroscope which has a spectroscope body in which positional relation between a light source and a diffraction grating is fixed, a detecting unit provided outside the spectroscope body, and a rotational transfer mechanism which performs rotational transfer of the spectroscope body and the detecting unit relatively. According to the spectroscope of Japanese Patent Application Laid-Open No. H07-198487, a spectrum can be performed without rotating a diffraction grating itself.
In addition, there is a Rowland circle which touches internally at a center of a diffraction grating made into concavity, and whose diameter is a curvature radius of the concave diffraction grating. When a slit is put on an arbitrary point on the Rowland circle, light is incident, and diffraction is caused by the concave diffraction grating, a spectrum without a chromatic aberration is imaged on the Rowland circle.
Also when rotational transfer of a spectroscope body, in which positional relation of a diffraction grating and a light source is fixed, and a detector is performed relatively like the spectroscope of Japanese Patent Application Laid-Open No. H07-198487, and also when rotational transfer of an outgoing slit on a Rowland circle is performed, it is able to enhance accuracy of a wavelength to be measured. However, since only the outgoing slit operates relatively, a position of the outgoing slit where diffraction efficiency becomes maximum is achieved only on a specific wavelength. Thus, since intensity of light which passes the outgoing slit has wavelength dispersion, depending on a wavelength, a noise component in light intensity becomes large, and there arises an issue that spectrum accuracy reduces.